Rotary cutting head for wrapping machine

ABSTRACT

A rotary cutting head for severing the packaging material webs in a wrapping machine includes an elongate saw type of knife blade mounted with parallelogram linkage on one of the cutting head shafts. A face cam, coaxial with the shaft, actuates a spring biased cam follower that is connected to the knife blade. The spring(s) during each revolution of the knife blade are sequentially armed by the cam, and then triggered or released to provide an instantaneous power impulse that rapidly swings the knife blade through the web.

Uite States atent Vande Castle Feb. 15, 1972 [54] ROTARY CUTTING HEADFOR WRAPPING MACHINE [72] Inventor: Jerome J. Vande Castle Green Bay,Wis.

[73] Assignee: FMC Corporation, San Jose, Calif [22] Filed: Dec. 22,1970 [21] Appl. No.: 5,077

[52] US. Cl ..83/322, 83/337, 83/338 [51] Int. Cl ..B26d 1/28 [58] FieldofSearch ..83/337, 338, 322;53/l82, 285

[56] References Cited UNITED STATES PATENTS 852,663 5/1907 Igou ..83/337X 322,552 7/1885 Northrup ..83/338 X 465,427 12/1891 Cox ..83/3371,583,393 5/1926 Coty ..83/337 2,051,453 8/1936 Mactaggart et al..3,057,239 10/1962 Teplitz 3,475,252 10/1969 White ..83/337 X PrimaryExaminer Frank T. Yost Attorney-F. W. Anderson and C. E. Tripp [5 7 1ABSTRACT A rotary cutting head for severing the packaging material websin a wrapping machine includes an elongate saw type of knife blademounted with parallelogram linkage on one of the cutting head shafts. Aface cam, coaxial with the shaft, actuates a spring biased cam followerthat is connected to the knife blade. The spring(s) during eachrevolution of the knife blade are sequentially armed by the cam, andthen triggered or released to provide an instantaneous power impulsethat rapidly swings the knife blade through the web.

2 Claims, 10 Drawing Figures PAIENTEBFEB 15 1972 3.641.857

SHEET 1 OF 5 INVENTOR. JEROME J. VANDE CASTLE BY Jw. W

ATTORNEYS PAENTEUFEB 15 I972 3.641.857

SHEET 5 0F 5 ROTARY CUTTING HEAD FOR WRAPPING MACHINE BACKGROUND OF THEINVENTION The present field of invention is in wrapping machines, andmore particularly concerns the cutoff portion of a rotary sealing andcutting head mechanism which transversely seals and severs the webmaterial enclosing a series of articles.

Web cutoff mechanisms used for paper and foil materials in presentwrapping machines include a rotary type in which a knife makes apressure cut against the web. The knife is mounted on a rotating shaft,driven in timed relation with the web, to enable the web cuttingoperation to be carried out at high speed. It is usually true, however,that the service life of the knife is short because the cutting edge ofthe knife must press through the web against a backup or anvil member.Thus, the cutting edge should have minimal pressure against the anvil,but this is difficult to maintain in practice, and the cutting edgerapidly dulls. Another type of rotary cutoff mechanism is a shear typewhich effects a scissor type of cut and is more efficient than thepressure-cut mechanisms. Most shear cutoff mechanisms, though, requireaccurate setup adjustments and rapidly get out of adjustment duringoperation.

Both the pressure-cut and rotary shear cutoff mechanisms require metalto metal contact of the knife blades with cooperating parts in order tosever the web, a situation which inevitably causes more knife wear thanif the knife contacts nothing but the web material. The presentinvention is directed to a rotary cutting head which operates in thismanner, that is, the cutting edge of the web severing knife contactsonly the web and has no contact whatever with any other structure.

SUMMARY OF THE INVENTION The concept of the present invention resides inRecognizing that knife blade wear results primarily from within themechanism itself rather than from the external work it does.

. Providing a sawtooth knife blade and knife blade actuating means forarming or preloading a power mechanism which, in effect, shoots theblade diagonally endwise through the web in a combined puncturing andsliding cutting action which severs webs which are unusually difficultto cut.

. Arming and triggering the power mechanism by the normal rotarymovement common to rotary web-cutoff mechanisms.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective of a knowntype of wrapping machine incorporating the rotary cutting head of thepresent invention.

FIG. 2 is a diagrammatic perspective illustrating a conventional cuttingand sealing head and its operation upon a tubular web enclosing spacedarticles.

FIG. 3 is an isometric view ofthe cutting head of the present invention.

FIG. 4 is an enlarged isometric view of a cam and cam fol lowermechanism shown in FIG. 3.

FIG. 5 is a top plan of the FIG. 3 apparatus at reduced scale.

FIG. 6 is an enlarged section taken along lines 6-6 on FIG. 5.

FIG. 7 is an enlarged section taken along lines 7-7 on FIG. 5.

FIG. 8 is a diagrammatic transverse section viewed in the direction ofweb movement, and illustrates an early stage of the knife operation.

FIG. 9 is a fragmentary section of the knife structure shown in FIG. 8,and illustrates a later operational condition.

FIG. 10 is a view similar to FIG. 8, but shows the completion ofthe websevering operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a known typeof wrapping machine 10, the general operating principles ofwhich aredisclosed in US. Pat. No. 2,546,721. In brief, the wrapping machine 10includes a pusher type of input conveyor 12, having an upper flight thatpropels a single file of spaced articles A into the machine. An overheadspool 14 carries a supply of wrapping material which, in the presentexample, is a single thickness film web W extending under a fixedforming plow 16. The forming plow transversely curls the web downwardlyaround the articles and is longitudinally sealed underneath to form atube 18, as shown in FIG. 2.

Laterally spaced conveying belts 20 (FIG. 1) grip and pull the entubedarticles downstream in the direction of the arrow 21, and the web tube18 is advanced to a rotary cutting head assembly C. A typical cuttinghead assembly may include upper and lower cutting head shafts 24 and 26(FIG. 2), respectively, which straddle the web tube 18 and counterrotatein synchronism with the movement of the web.

Heated crimping jaws 28 and 30 are mounted on the shafts 24 and 26 totransversely heat seal the film between adjacent articles. Additionally,the gripping jaws are conventionally as sociated with web severingmechanism, not shown in FIG. 2. which severs the web to produce anoutput of individual packages P that are then carried from the machine,such as by a lateral discharge conveyor at 32 (FIG. I).

The present invention concerns an improved web severing mechanism 34(FIG. 3) which is incorporated with the upper cutting head shaft 24(FIG. I) of the cutting head assembly C. Before describing the structureof the invention, it should be noted that conventional or existingstructure includes intermeshed gears 36 and 38 on the cutting headshafts 24 and 26 to rotate the crimping jaws 28 and 30 in timed relationto each other and to the motion of the web. The other end of the lowershaft 26 is fixed in the frame of the wrapping machine, and the adjacentend of the upper shaft 24 is mounted in a block 40 which is mounted in aslide frame 42 (FIG. 1). Springs 44 bias the block 40 toward itsoperating position, and also allow upward displacement of the uppershaft 24 in the event the machine malfunctions and an article is betweenthe crimping jaws when they close. As thus far described, the structureis known in prior art wrapping machines, except for the web severingmechanism 34.

The crimping jaws 28 and 30 are each provided with a longitudinalcentral slot 35 for operating clearance of whatever web severing meansare used, and the web severing mechanism of the present invention isoperable within the same space limits of the slots. With continuedreference to FIG. 3, the slot 35 in the upper crimping jaw 28 providesoperating clearance for a saw tooth knife blade 38 which is movablebetween an inactive or retracted position totally concealed in the slot35, and an active or projected position in which the cutting teeth lieoutward of the edges of the slot. FIG. 3 illustrates a top dead centeror intermediate position since the knife is in active position only whenit is at bottom dead center, and is in a fully retracted position justprior to arriving at bottom dead center. In active position, theprojecting knife blade enters the clearance slot 35 of the lowercrimping jaw 30.

One convenient and inexpensive form of knife is a length of commerciallyavailable presharpened bandsaw stock. To facilitate the penetration andcutting of strong wrapping materialsin a manner later described-one sideof the teeth are preferably ground so that the teeth taper, in endprofile, from their apexes as shown in FIG. 6. Knife blade 38 (see alsoFIG. 8) is clamped between two identical knife holder arms 40, one ofwhich is provided with threaded apertures for clamping screws 42 thatpass through the other knife holder arm and through apertures in theknife blade. As best seen in FIG. 8, the knife holder arms 40 haveoutwardly curved end portions and are pivoted at 44 and 46,respectively, to parallelogram links 48 and 50 so that during endwisemovement of the knife holder arms 40, the knife blade teeth aremaintained parallel to the axis of the cutting head shaft 24.

The parallelogram link 48 is pivotally mounted on a pivot pin 52 that isheld in a mounting block 54 which is bolted to the cutting head shaft24. In similar manner, the parallelogram link 50 is pivotally mounted ona pivot pin 56 which is held in a mounting block 58 that is bolted tothe cutting head shaft 24. The latter mounting block includes a knifeblade arming and triggering mechanism 60 which utilizes the rotarymotion of the cutting head shaft 24 to power and release (arm andtrigger) the knife blade 38.

A circular face cam 62 is bolted in rotatively adjusted position to theslide frame block 40, and functions to load a pair of compressionsprings 64 that arm the knife blade, and to substantiallyinstantaneously release the springs to trigger the knife blade for itsweb severing function. For this purpose, the cam 62 (FIG. 4) actuates acam follower 65 and is provided with a camming surface that has auniform rise from a low portion 66 to a high portion 68, and anintermediate sharp dropoff or triggering portion 70.

The axial motion of the cam follower 65 along the shaft 24 actuates aT-shaped follower arm 72 which is provided with a guide shaft 74 that isslidable in the mounting block 58. A key 76 maintains the orientation ofthe follower arm 72 relative to the mounting block 58. A crossmember 78of the follower arm is apertured for sliding motion over two springguide rods 80 which each project from the flange portion ofa rod bracket82 (FIG. 3) that is secured to the mounting block 58.

In order to transmit the motion of the follower arm 72 to the knifeblade 38, the free end of the shaft 74 is provided with a pivot pin 84connecting a pair of links 86 to the adjacent end portions of the knifeblade holders 40. Due to the parallelogram link mounting for the knifeblade, it will be evident that the knife blade 38 is thrust bothradially and axially of the cutting head shaft 24 in a swinging motion,and that the knife blade motion occurs when the cam follower 65 dropsoff the high cam portion 68 to the low cam portion 66. Stateddifferently, the teeth of the knife blade 38 move approximatelydiagonally toward, through and across the plane of the web, whereby thesharp teeth easily penetrate and sever relatively strong web materialsbecause the cutting action produces both a puncture action and a slidingcutting action. Further, the initial motion of the knife blade is moreradial than axial before the parallelogram links 48 and 50 areperpendicular to the shaft 24. Therefore, the puncturing of the web isthe predominant initial web-cutting action, and webs of unusual strengthcan readily be penetrated for the final severing action as the knifeteeth move in a direction more parallel to the web. An important aspectof the knife blade action, it will be recognized, is its very rapidacceleration due to the nearly instantaneous release ofthe power impulsestored in the springs 64.

FIGS. 8-10 illustrate successive stages in arming and triggering theknife blade 38. The knife blade arming and triggering mechanism 60 (FIG.8) is partially armed because the cam follower 65 is midway on the cam62 at top dead center. As the cam follower moves downward over theterminal rise portion of the cam 62, it slides the follower arm 72toward the knife blade 38 and further compresses the springs 64. At thesame time, the follower arm 72 swings the parallelogram links 48 and 50away from the cam 62, thus retracting the knife holder arms 40 radiallyinward so that the teeth of the knife blade 38 (FIG. 9) are concealed inthe upper crimping jaw 28. Meanwhile, the heated crimping jaws 28 and 30have moved into heat sealing relation with the web tube 18, as shown inFIG. 2. With the web tube still gripped by the crimping jaws as shown inFIG. 10, the cam follower 65 is rapidly retracted over the triggeringportion 70 of the cam 62 because at this point the armed springs 64 arefree to resume their initial compression. Accordingly, the follower arm72 is triggered to substantially instantaneously swing the knife holderarms 40 (FIG. 9) toward the cam 62, and the knife blade 38 shootsthrough and severs the web tube 18 with the puncturing and sliding-cutmotion reviousl described. Precise adjustments II] the timing of thenrfe bla e action to the motion of the web is readily accomplished byrotatively adjusting the fixed position of the cam 62.

As previously mentioned, an important advantage of the web severingmechanism of the present invention is that the power impulse for thecutting action is derived from the stored energy of the arming springs64, and that this energy is substantially instantaneously released todrive or shoot the knife through the web. By this means, the knife bladewill easily penetrate and sever very strong web materials, includinglaminates which may incorporate metal foils, layers of paper and extratough plastic films. Accordingly, a further important aspect of thepresent inventive concept is utilizing the rotary motion of one of thecutting head shafts for sequentially arming and triggering a powermechanism which actuates the knife blade; in contrast to presently knowncam-driven web severing devices, the rotary shear of the presentinvention derives its effectiveness from the very rapid acceleration ofthe knife blade, and from the puncturing and sliding-cut mode of knifeblade operation.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

I claim:

1. In a wrapping machine, a rotary cutting head comprising a rotatabledriven shaft extending across a web to be severed, a fixed circular facecam coaxial with one end portion of said shaft, said cam being providedwith a circular cam surface having a uniform rise with a rapid cutoffportion between the high and low points, an elongate longitudinallyslotted crimping jaw mounted on said shaft, a knife blade positioned inthe slot of said crimping jaw, means mounting said blade to said shaftfor movement of the cutting edge of the blade into and out of said slot,and spring biased arming means mounted on said shaft adjacent one end ofsaid knife blade and connected to said blade mounting means, said lattermeans including a cam follower engaged with said cam surface for loadingthe biasing spring during rotary movement of said shaft and said rapidcutoff portion of said cam releasing the biasing spring to provide asubstantially instantaneous power impulse to said knife blade.

In a wrapping machine, a rotary cutting head comprising a rotatabledriven shaft extending across a web of wrapping material to be severed,a circular face cam coaxial with one end portion of said shaft, said cambeing provided with a circular cam surface having a rapid cutoff betweenhigh and low points thereof, a knife blade carried by said shaft,linkage means mounting said knife blade on said shaft for movementcarrying the cutting edge of the blade radially and axially of saidshaft, and cam follower means mounted on said shaft in termediate saidknife blade and said face cam, said cam follower means including afollower roller engaging said cam surface and a spring urging saidfollower roller toward said cam surface, said cam loading said biasingspring during rotary movement of said shaft to provide stored powerwhich is released to substantially instantaneously actuate said knifeblade when said cam follower roller drops off the cutoff portion of saidcam.

1. In a wrapping machine, a rotary cutting head comprising a rotatabledriven shaft extending across a web to be severed, a fixed circular facecam coaxial with one end portion of said shaft, said cam being providedwith a circular cam surface having a uniform rise with a rapid cutoffportion between the high and low points, an elongate longitudinallyslotted crimping jaw mounted on said shaft, a knife blade positioned inthe slot of said crimping jaw, means mounting said blade to said shaftfor movement of the cutting edge of the blade into and out of said slot,and spring biased arming means mounted on said shaft adjacent one end ofsaid knife blade and connected to said blade mounting means, said lattermeans including a cam follower engaged with said cam surface for loadingthe biasing spring during rotary movement of said shaft and said rapidcutoff portion of said cam releasing the biasing spring to provide asubstantially instantaneous power impulse to said knife blade. hIn awrapping machine, a rotary cutting head comprising a rotatable drivenshaft extending across a web of wrapping material to be severed, acircular face cam coaxial with one end portion of said shaft, said cambeing provided with a circular cam surface having a rapid cutoff betweenhigh and low points thereof, a knife blade carried by said shaft,linkage means mounting said knife blade on said shaft for movementcArrying the cutting edge of the blade radially and axially of saidshaft, and cam follower means mounted on said shaft intermediate saidknife blade and said face cam, said cam follower means including afollower roller engaging said cam surface and a spring urging saidfollower roller toward said cam surface, said cam loading said biasingspring during rotary movement of said shaft to provide stored powerwhich is released to substantially instantaneously actuate said knifeblade when said cam follower roller drops off the cutoff portion of saidcam.